//Given a binary tree, determine if it is height-balanced. 
//
// For this problem, a height-balanced binary tree is defined as: 
//
// 
// a binary tree in which the left and right subtrees of every node differ in he
//ight by no more than 1. 
// 
//
// 
// Example 1: 
//
// 
//Input: root = [3,9,20,null,null,15,7]
//Output: true
// 
//
// Example 2: 
//
// 
//Input: root = [1,2,2,3,3,null,null,4,4]
//Output: false
// 
//
// Example 3: 
//
// 
//Input: root = []
//Output: true
// 
//
// 
// Constraints: 
//
// 
// The number of nodes in the tree is in the range [0, 5000]. 
// -104 <= Node.val <= 104 
// 
// Related Topics 树 深度优先搜索 递归 
// 👍 681 👎 0


package leetcode.editor.cn;

import java.util.LinkedList;
import java.util.Queue;

//Java：Balanced Binary Tree
class P110BalancedBinaryTree {
    public static void main(String[] args) {
        Solution solution = new P110BalancedBinaryTree().new Solution();
        // TO TEST
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        root.right = new TreeNode(2);
        root.left.left = new TreeNode(3);
        root.left.right = new TreeNode(3);
        root.left.right.left = new TreeNode(4);
        root.left.right.right = new TreeNode(4);
        System.out.println(solution.isBalanced(root));
    }
    //leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     * int val;
     * TreeNode left;
     * TreeNode right;
     * TreeNode() {}
     * TreeNode(int val) { this.val = val; }
     * TreeNode(int val, TreeNode left, TreeNode right) {
     * this.val = val;
     * this.left = left;
     * this.right = right;
     * }
     * }
     */
    class Solution {
        public boolean R(TreeNode root) {
            if (root != null) {
                int left = DepthOfTree(root.left);

                int right = DepthOfTree(root.right);
                return Math.abs(left - right) >= 2 ? false : true &&

                        R(root.left) && R(root.right);
            } else {
                return true;
            }

        }

        public int DepthOfTree(TreeNode treeNode) {
            if (treeNode == null) {
                return 0;
            }
            return Math.max(DepthOfTree(treeNode.left) + 1, DepthOfTree(treeNode.right) + 1);
        }
        public boolean isBalanced(TreeNode root){
            Queue<TreeNode> q=new LinkedList<>();
            q.offer(root);
            TreeNode pre=root;
            while(q.size()>0){
                int size=q.size();
                for(int i=0;i<size;i++){
                    TreeNode node=q.poll();
                    //前一个没有序号，后面一个有
                    if(pre==null&&node!=null){
                        return false;
                    }
                    if(node!=null){
                        q.offer(node.left);
                        q.offer(node.right);
                    }
                    pre=node;
                }
            }
            return true;


        }
    }
//leetcode submit region end(Prohibit modification and deletion)

}